JP5082726B2 - Elastic wave device - Google Patents

Description

  The present invention relates to an elastic wave device, and more particularly to an elastic wave device such as a surface acoustic wave filter and a boundary acoustic wave filter.

  As a surface acoustic wave device such as a surface acoustic wave filter or a boundary acoustic wave filter, a small and low profile CSP (chip size package) type has been proposed.

For example, in the CSP (chip size package) type surface acoustic wave filter 101 shown in FIG. 5, the piezoelectric substrate 102 is mounted face-down so that the lower surface on which the resonator electrode 103 c is formed faces the package substrate 110. The input / output electrode 103 a formed on the lower surface of the piezoelectric substrate 102 is connected to the connection pad 109 via the conductive adhesive 108, and the connection pad 109 is connected to the external extraction electrode 113 via the via electrode 111. ing. On the outer periphery of the lower surface of the piezoelectric substrate 102, a grounding electrode 103b formed so as to surround the resonator electrode 103c is connected to a connection pad 109 of the package substrate 110 via a conductive adhesive 108. A metal thin film 112 is formed on the upper surface and side surfaces of the piezoelectric substrate 102, and a reduction in size and height is realized.
JP 2000-31127 A

  However, in this surface acoustic wave filter, since the grounding electrode 103b is only connected to the metal thin film 112, if the piezoelectric substrate 102 is further reduced in size, the grounding cannot be sufficiently obtained, and the out-of-band attenuation characteristic of the filter. There are problems such as worsening. If ground via electrodes and external electrodes are formed on the package substrate 110 in order to strengthen the ground, the parasitic capacitance inside the package substrate 110 increases and the insertion loss of the filter deteriorates. Further, if the package substrates are stacked and wired inside, the layout can be made so that the gap between the via electrodes is widened. However, this increases the size and height of the package substrate 110.

  In view of such circumstances, the present invention intends to provide an elastic wave device that can reinforce the ground even if it is reduced in size and height.

  In order to solve the above-mentioned problems, the present invention provides an elastic wave device configured as follows.

The acoustic wave device includes: (a) a piezoelectric substrate and a package substrate each having one main surface facing each other with a space; and (b) forming the one main surface of the piezoelectric substrate along the periphery of the one main surface. and ground pads, (c) said formed from inside the ground pad in the one main surface of the piezoelectric substrate, a conductor pattern including IDT electrodes and output pads, (d) said one main of the package substrate An input / output electrode formed on the surface corresponding to the input / output pad; and (e) formed on the one main surface of the package substrate corresponding to the ground pad and extending to the periphery of the one main surface. a ground electrode for standing, (f) said are respectively disposed between the ground pad and the output pad and the ground electrode and the output electrode, the ground pad and the input path And a conductive adhesive for electrically connecting the grounding electrode and the input / output electrode, respectively, and ( g ) formed on the other main surface of the package substrate so as to extend to the periphery of the other main surface. ( H ) an input / output electrode pattern formed corresponding to the input / output electrode on the other main surface of the package substrate; ( i ) penetrating the package substrate; and through conductor which electrically connects the said input-output electrode pattern on the other hand that the entering-output electrodes formed on the major surface formed on the other main surface of the package substrate, (j) the piezoelectric substrate and other hand the principal surface of, extending between said one main surface of the piezoelectric substrate and a side surface extending between the other main surface, the one main surface and the other main surface of the package substrate I'll cover the side A conductive film electrically connected to the ground electrode formed on the one main surface of the package substrate and the ground electrode pattern disposed on the other main surface of the package substrate; ( K ) covering the other main surface of the package substrate, and having an opening through which the input / output electrode pattern and the ground electrode pattern formed on the other main surface of the package substrate are exposed to the outside. And a dielectric or insulating coating layer.

  According to the above configuration, the conductive film covering the other main surface and the side surface of the piezoelectric substrate is extended to the side surface of the package substrate, and formed on the other main surface of the package substrate and the ground electrode formed on the one main surface of the package substrate. By electrically connecting to the grounding electrode pattern thus formed, the grounding pad of the piezoelectric substrate can be grounded to the outside of the surface acoustic wave device via the grounding electrode pattern. The grounding can be strengthened without increasing the number of through conductors for electrically connecting the ground electrode and the grounding electrode pattern to the package substrate.

  According to the above configuration, the size and the height can be reduced by face-down mounting in which the piezoelectric substrate and the package substrate are joined to face each other. Even if the earth is strengthened, the number of through conductors for grounding is not increased on the package substrate, so that the parasitic capacitance inside the package substrate is not increased and the insertion loss of the filter is not deteriorated. By covering the surface of the piezoelectric substrate with a conductive film, it is possible to shield outflow radio waves, improve heat dissipation, and improve pyroelectric resistance and electrostatic resistance.

  Preferably, the grounding electrode pattern extends from the other main surface of the package substrate to the side surface of the package substrate.

  In this case, since the grounding electrode pattern exceeds the outer peripheral edge of the other main surface of the package substrate and reaches the side surface of the package substrate on which the conductive film is formed, the grounding electrode pattern is formed on the other main surface of the package substrate. Compared with the case where only the outer peripheral edge is reached, the electrical connection with the conductive film formed on the side surface of the package substrate can be made more reliable, and the reliability is improved.

  Preferably, a groove is formed on the side surface of the package substrate, and a side electrode is formed in the groove. The side electrode is electrically connected to the ground electrode pattern.

  In this case, the area where the conductive film and the external grounding electrode pattern are connected increases, the conductive film and the external grounding electrode pattern are more reliably connected, and the reliability is improved.

  Each of the above configurations is particularly suitable for a surface acoustic wave device (such as a surface acoustic wave filter) that uses a surface acoustic wave propagating on the one principal surface of the piezoelectric substrate.

  According to the present invention, the grounding can be strengthened even if the elastic wave device is reduced in size and height.

  Hereinafter, examples of the present invention will be described with reference to FIGS.

  <Example 1> The elastic wave filter 2 of Example 1 is demonstrated, referring FIGS. 1-4.

  FIG. 1 is a cross-sectional view of the acoustic wave filter 2. FIG. 2A is a surface view of the package substrate 20 in the acoustic wave filter 2. FIG. 2B is also a back view.

  As shown in FIG. 1, in the acoustic wave filter 2, the piezoelectric substrate 10 and the package substrate 20 are opposed to each other with a space 13, and their peripheral portions are joined. The acoustic wave filter 2 is, for example, a surface acoustic wave filter.

  As will be described in detail later, the piezoelectric substrate 10 has a ground pad formed along the peripheral edge of the lower surface 14 on the lower surface 14 facing the package substrate 20. A conductor pattern including a wiring connecting the two is formed.

  In the package substrate 20, a ground electrode 40 is formed on the upper surface 22 facing the piezoelectric substrate 10, as shown in FIG. 2A, corresponding to the ground pad formed on the lower surface 14 of the piezoelectric substrate 10. . Input / output electrodes 30a, 30b, and 30c are formed corresponding to the input / output pads formed on the lower surface 14 of the piezoelectric substrate 10. The ground electrode 40 and the input / output electrodes 30a, 30b, and 30c formed on the upper surface 22 of the package substrate 20 and the ground pad and the input / output pad formed on the lower surface 14 of the piezoelectric substrate 10 are respectively conductive such as metal bumps. They are joined and electrically connected via a bonding adhesive.

  As shown in FIG. 2B, the package substrate 20 is formed with a ground electrode pattern 42 and input / output electrode patterns 32a, 32b, and 32c on the lower surface 24 opposite to the piezoelectric substrate 10. The ground electrode pattern 42 extends to the peripheral edge 25 of the lower surface 24 of the package substrate 20. The input / output electrode patterns 32a, 32b, and 32c are, as shown in FIG. 1, input / output electrodes 30a, 30b, and 30c formed on the upper surface 22 of the package substrate 20 by vias 28 penetrating the package substrate 20, respectively. Electrically connected.

  As shown in FIG. 1, a conductive film 60 is formed so as to cover the surface of the piezoelectric substrate 10, that is, the upper surface 12 and the side surface 16, and the side surface 26 of the package substrate 20. The conductive film 60 is electrically connected to the ground electrode 40 formed on the upper surface 22 of the package substrate 20, and further, as shown exaggeratedly in the bottom view of FIG. The peripheral edge 25 is electrically connected to the ground electrode pattern 42.

  The ground electrode 40 formed on the upper surface 22 of the package substrate 20 and the ground electrode pattern 42 formed on the lower surface 24 of the package substrate 20 are electrically connected via the conductive film 60 formed on the side surface 26 of the package substrate 20. Therefore, the package substrate 20 includes a through conductor, such as a via or a through hole, for electrically connecting the ground electrode 40 formed on both surfaces 22 and 24 of the package substrate 20 and the ground electrode pattern 42. There is no need to form holes.

  Although not shown in FIG. 1, a coating layer is formed on the bottom surface (lower surface in the figure) of the acoustic wave filter 2, and the external electrodes are exposed.

  That is, as shown in the bottom view of FIG. 3B, a dielectric or insulator is applied to the lower surface 24 of the package substrate 20 on which the input / output electrode patterns 32a, 32b, 32c and the ground electrode pattern 42 are formed. The covering layer 50 is formed by partially coating using it. Openings 50a to 50e are formed in the coating layer 50, and a part of the input / output electrode patterns 32a, 32b, and 32c and a part of the ground electrode pattern 42 are exposed from the openings 50a to 50e. As shown in the bottom view of FIG. 3 (c), the bottom surface of the elastic wave filter 2 is externally exposed by the portions exposed from the openings 50a to 50e of the input / output electrode patterns 32a, 32b, and 32c and the ground electrode pattern 42. Input / output electrodes 32x, 32y, 32z and external ground electrodes 42x, 42y are formed.

  The conductive film 60 covering the upper surface 12 and the side surface 16 of the piezoelectric substrate 10 extends to the side surface of the package substrate 20 and is electrically connected to the ground electrode pattern 42 formed on the lower surface 24 of the package substrate 20. As a result, the grounding can be strengthened without increasing vias and through holes in the package substrate 20.

  The ground electrode pattern 42 is electrically connected to the conductive film 60 at the periphery 25 of the lower surface 24 of the package substrate 20. In order to connect more securely to the conductive film 60, the ground electrode pattern 42 extends as much as possible to the outer peripheral portion of the lower surface 24 of the package substrate 20, and the ground electrode pattern 42 of the peripheral edge 25 of the lower surface 24. It is desirable to lengthen the portion where the distance reaches as long as possible and to lengthen the connection length with the conductive film 60.

  The ground electrode pattern 42 preferably extends beyond the peripheral edge 25 of the lower surface 24 of the package substrate 20 to the side surface 26 of the package substrate 20. In this case, the connection area between the grounding electrode pattern 42 and the conductive film 60 is increased, and the grounding electrode pattern 42 and the conductive film 60 can be more reliably bonded to improve the reliability.

  Furthermore, if a castellation (side groove) is formed on the side surface 26 of the package substrate 20 and a side electrode is formed in the castellation, the connection length and the connection area between the conductive film 60 and the ground electrode pattern 42 are increased. The conductive film 60 and the grounding electrode pattern 42 can be more reliably bonded to further improve the reliability. The castellation can be formed by forming a through hole in advance so as to protrude from the dicing line in the collective substrate and dicing so that a part of the through hole remains on the side surface of the package substrate.

  Next, a method for manufacturing the elastic wave filter 2 will be described. Hereinafter, a case where both the piezoelectric substrate 10 and the package substrate 20 are joined in a collective substrate state and then divided into individual pieces will be described. However, one or both of the piezoelectric substrate 10 and the package substrate 20 are separated into individual pieces. It can also be produced by bonding in a state.

Using a metal mainly composed of Al on a piezoelectric wafer such as LiTaO ₃ or LiNbO ₃ , as shown in the plan view of FIG. 4, an element portion including an IDT electrode and a reflector, an input / output pad, and a ground A plurality of GND patterns including pads and wirings connecting them are formed in a lump. A rectangular region virtually indicated by a white chain line corresponds to one piezoelectric substrate 10. The GND pattern is a black portion having a large area. Comb-shaped IDT electrodes and reflectors, and a substantially circular input / output pad are arranged in a white area surrounded by the GND pattern.

  The GND pattern extends along the peripheral edge (white chain line) in each piezoelectric substrate, extends to the outside beyond the peripheral edge, and is formed so as to be connected between unit patterns arranged on the wafer. It is designed so that the outer periphery of the subsequent piezoelectric chip (piezoelectric substrate 10) is entirely surrounded by the GND pattern. All GND wirings from the IDT electrode are connected to a GND pattern provided on the outer periphery of the chip.

  The GND pattern on the outer periphery of the piezoelectric chip is also used as a ground pad for sealing. Therefore, it is preferable to thicken a metal film such as Al or Au via an adhesion layer such as Ti, Pt, or Pd in a portion corresponding to the ground pad as a measure for improving the bonding strength when applying thermal stress.

  A piezoelectric wafer on which an IDT electrode, a GND electrode pattern, and the like are formed is face-down bonded to a package (including LTCC) containing ceramic as a main component using metal bumps. Face down bonding requires that the hollow structure on the IDT electrode formed on the piezoelectric chip requires airtightness, and that the GND electrode of the piezoelectric chip must be electrically connected to the GND electrode of the package. Use low resistance metal.

  An organic substrate (printed substrate) whose main material is glass cloth or epoxy resin can also be used for the package. In this case, the material cost used for the package can be reduced. Moreover, it is excellent in cracking strength when the package thickness is reduced. The degree of freedom in selecting the relative dielectric constant of the package material is increased.

  In the package, as shown in FIG. 2, only the input / output electrodes 30a, 30b, 30c of the signal terminals are electrically connected to the signal electrodes 32a, 32b, 32c on the lower surface 24 of the package through vias 28 or through holes in the package. As shown in FIG. Further, the ground electrode 40 is formed in advance so as to face the GND pattern formed on the outer periphery of the piezoelectric chip. Similarly to the piezoelectric chip, the package ground electrode 40 and the ground electrode pattern 42 on the opposite surface are formed in advance so as to be connected between unit patterns arranged on the package.

  After the face-down bonding, the piezoelectric wafer and the package are collectively diced into pieces of the elastic wave filter 2.

  After dicing, as shown in FIG. 1, the outer peripheral surface (other than the lower surface 14 on which the IDT electrode is formed) 12 and 16 of the cut piezoelectric chip 10 and part or the entire side surface 26 of the package substrate 20 are made of metal or The conductive film 60 is formed by coating with a conductive material, and electrical connection is established with the metal bumps used to connect the piezoelectric wafer (piezoelectric substrate 10) and the package (package substrate 20). The coating method is preferably a metal plating or vapor deposition method with excellent adhesion.

  As a result, the signal electrode is connected to the product terminals 32x, 32y, 32z, 42x, and 42y on the package lower surface 24 by the via 28 in the package and the GND electrode by the conductive film 60 on the side surface 26 of the package substrate 20. It will be.

  Thereafter, as shown in FIG. 3B, an insulating film made of a dielectric material or an organic material is partially coated on the lower surface 24 and the side surface 26 of the package substrate 20 to form a covering layer 50, as shown in FIG. ) To obtain the required electrode shape.

  As described above, the elastic wave filter 2 having a small size, a low profile, and good electrical characteristics can be provided at low cost.

  Although a longitudinally coupled resonator type filter for balanced output has been described as an example, the same configuration is applied to an elastic wave filter that requires a hollow structure on a laterally coupled type or ladder type IDT electrode. Can do.

  The elastic wave filter 2 can secure a pattern necessary for the GND wiring on the outer periphery of the chip, and is effective for strengthening the GND when downsizing. Since the GND wiring is shared on the outer periphery of the chip, a stacked package is not necessary, which is advantageous for low profile and low cost.

  By using the via 28 only for the signal terminal, the design freedom of the chip design is increased, and the parasitic capacitance in the package is reduced, which is effective for the deterioration of the insertion loss.

  By covering the outer periphery of the chip with a GND pattern, (a) the influence on the filter due to electromagnetic noise from peripheral components can be reduced, and (b) the pyroelectric resistance is improved because the amount of charge in the pyroelectric product is reduced. (C) Electrostatic resistance is improved, (d) heat dissipation is improved, and power resistance is improved.

  <Summary> As described above, even if the elastic wave device is reduced in size and height, grounding can be strengthened. Further, since the ground vias and through holes are not increased in the package substrate, the parasitic capacitance inside the package substrate is not increased and the insertion loss of the filter is not deteriorated. By covering the surface of the piezoelectric substrate with a conductive film, it is possible to shield outflow radio waves, improve heat dissipation, and improve pyroelectric resistance and electrostatic resistance.

  The present invention is not limited to the above-described embodiment, and can be implemented with various modifications.

It is sectional drawing of an elastic wave filter. Example 1 It is a front and back view of a package substrate in an elastic wave filter. Example 1 It is the bottom view of the state which exposed the electrode pattern of the acoustic wave filter, (b) The bottom view of the state which provided the coating layer, (c) The bottom view. Example 1 It is a top view of a wafer. Example 1 It is sectional drawing of a surface acoustic wave filter. (Conventional example)

Explanation of symbols

2 Elastic wave filter (elastic wave device)
10 Piezoelectric substrate 12 Upper surface (the other main surface)
14 Lower surface (one main surface)
16 Side 20 Package substrate 22 Upper surface (one main surface)
24 Lower surface (the other main surface)
25 Perimeter 26 Side 28 Via (through conductor)
30a, 30b, 30c Input / output electrodes 32a, 32b, 32c Input / output electrode patterns 32x, 32y, 32z External input / output electrodes 40 Ground electrodes 42 Ground electrode patterns 42x, 42y External ground electrodes 50 Coating layers 50a, 50b, 50c, 50d, 50e opening 60 conductive film

Claims (4)

A piezoelectric substrate and a package substrate each having one main surface facing each other with a space;
A grounding pad formed along the periphery of the one main surface of the one main surface of the piezoelectric substrate;
A conductor pattern including an IDT electrode and an input / output pad formed inside the ground pad on the one main surface of the piezoelectric substrate;
On the one main surface of the package substrate, input / output electrodes formed corresponding to the input / output pads;
On the one main surface of the package substrate, a ground electrode formed corresponding to the ground pad and extending to the periphery of the one main surface;
The ground pad and the input / output pad are disposed between the ground electrode and the input / output electrode, respectively, and electrically connect the ground pad and the input / output pad to the ground electrode and the input / output electrode. Conductive adhesive,
An electrode pattern for grounding formed to extend to the periphery of the other main surface of the other main surface of the package substrate;
An input / output electrode pattern formed on the other main surface of the package substrate corresponding to the input / output electrodes;
Penetrating the package substrate, electrically connecting the other hand front formed on the main surface entry output electrode and the input electrode pattern formed in said second main surface of the package substrate of the package substrate A through conductor,
The other side main surface of the piezoelectric substrate, and a side surface extending between the one main surface and the other main surface of the piezoelectric substrate, between the one main surface and the other main surface of the package substrate An electrical connection to the ground electrode formed on the one main surface of the package substrate and the ground electrode pattern disposed on the other main surface of the package substrate. A conductive film connected to the
A dielectric or insulating material that covers the other main surface of the package substrate and has an opening that exposes the input / output electrode pattern and the ground electrode pattern formed on the other main surface of the package substrate to the outside. A body covering layer;
An elastic wave device comprising:   2. The acoustic wave device according to claim 1, wherein the ground electrode pattern is extended from the other main surface of the package substrate to the side surface of the package substrate. A groove is formed on the side surface of the package substrate, and a side electrode is formed in the groove,
The acoustic wave device according to claim 1, wherein the side electrode is electrically connected to the ground electrode pattern.   The surface acoustic wave device according to claim 1, wherein the surface acoustic wave propagates on the one principal surface of the piezoelectric substrate.

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